U.S. Pat. No. 5,237,987 discloses a ventilating apparatus having a mixing and metering device for medical gases for ventilating a patient.
The known ventilating apparatus includes a control arrangement with which the user can set and monitor the ventilating mode and the ventilating gas pressure, the gas composition and the ventilating gas flow. A display screen is a component of the control arrangement with which the parameters set according to the menu structures are displayed to the user as input quantities. In the case that parameters are to be changed, the user can first call up the parameter to be changed in one of the menu structures using a centrally positioned rotatable knob. The parameter to be changed can be selected by pressure on an acknowledgment switch. Inside of a menu window, the parameter can then be varied numerically and the new parameter can now be assumed by the control arrangement as a new setting value for the ventilating apparatus by applying pressure to the acknowledgment switch. Thereafter, another parameter from the menu structure can be selected and changed if required. A further switch enables a switchover between a menu structure that displays parameters and a menu structure that changes parameters.
A disadvantage of the known ventilating apparatus is that, by the numerical change of a selected parameter and inadvertent actuation of the acknowledgment switch, a correction of the parameter assumed in error is not possible directly. Instead, the incorrectly set parameter must first be again selected in order to then be numerically set to the desired value. This complicates handling the apparatus especially in situations of stress.